split up vs fragment

split up and fragment both are nouns.

Word	Noun	Adjective	Verb	Adverb
split up	Yes	No	Yes	No
fragment	Yes	No	Yes	No

As verbs, fragment is a hyponym of split up; that is, fragment is a word with a more specific, narrower meaning than split up:

split up (noun)	fragment (noun)
an increase in the number of outstanding shares of a corporation without changing the shareholders' equity	a broken piece of a brittle artifact
	an incomplete piece
	a piece broken off or cut off of something else

split up (verb)	fragment (verb)
become separated into pieces or fragments	break or cause to break into pieces
get a divorce; formally terminate a marriage
discontinue an association or relation; go different ways
separate into parts or portions